Yield and Protein Response of Wheat Cultivars to Polymer‐Coated Urea and Urea

Abstract

Discount payments associated with low grain protein concentration in hard red spring wheat (HRSW, Triticum aestivum L.) in recent years has increased interest for using controlled-release N fertilizers to increase protein concentration while maintaining optimal grain yields. Field experiments were conducted during 6 site-years in Minnesota from 2007 to 2009 to examine eff ects of a polymer-coated urea (PCU, Environmentally Smart Nitrogen [ESN], Agrium Inc., Calgary, AB, Canada) and non-coated urea on grain yields and protein concentrations of two HRSW cultivars, Alsen and Knudson, that vary in grain yield and protein concentration potentials. Polymer-coated urea and urea were applied in spring at six rates that supplied 0 to 110 kg N ha -1 in 2007 and 0 to 168 kg N ha -1 in 2008 and 2009. Because of genetic diff erences, Knudson produced greater grain yield than Alsen in environments (site-years), which were cooler and drier early in the growing season and the yield diff erences between the two cultivars increased with increasing N rates. In the same environment, PCU decreased grain yield compared with urea, which could be related to a reduced N release early in the growing season. Compared with urea, higher N (at Zadoks scale 85) and protein concentrations (at Zadoks scale 92) with PCU were observed due to increased N availability later during the growing season. To increase wheat protein concentrations from using PCU, future studies should evaluate diff erent mixtures of PCU and urea.

Nitrogen Fertilizer Sources and Application Timing Affects Wheat and Inter-Seeded Red Clover Yields on Claypan Soils

“…Wheat grain yield response to fall-applied N sources during years (2004, 2005, and 2007) with medium-to poorly-drained soils ranked PCU > AN > U + NBPT > urea ≥ UAN (Figure 2A). All N sources increased yield as N rate increased, similar to other research [15,36], but wheat yield was unlikely to increase when inorganic soil test N exceeded 120 kg N ha −1 [37]. PCU , which were below average for the region [2].…”

“…There was no significant difference in wheat biomass among N sources in 2004 and 2007, but wheat biomass was ranked PCU > AN = UAN = U + NBPT > urea in 2005 (Table 2). In Minnesota, PCU had no effect on wheat biomass in spring wheat [15], while in North Carolina lower wheat biomass was observed with PCU compared to other N sources [13]. No differences were found among fall-applied N sources on wheat grain moisture or plant tissue N concentration.…”

“…The spring application of PCU was expected to result in lower wheat yields [14,15]; however, spring applied PCU was relatively early which allowed more time for N release and greater overall yields. Otherwise, the recommended blend ratio of PCU to a fast-release N source should decrease to a 75:25 or 50:50 ratio lest wheat yields decrease [16].…”

“…Nitrate leaching is a greater risk when these N sources are applied in the fall. Several studies have evaluated response to enhanced-efficiency N fertilizer in wheat [13][14][15][16], canola (Brassica napus L.) [17,18], and barley (Hordeum vulgare L.) [19]. Wheat yield response varied based on management, application timing, application rate, and environmental conditions.…”

“…Wheat yield response varied based on management, application timing, application rate, and environmental conditions. Studies of small grains show that, in addition to yield impacts, protein concentration with PCU was similar or increased compared to urea [15,19]. It is critical to understand the possible utility of enhanced efficiency fertilizer sources in order to properly integrate this technology into Midwestern wheat production systems.…”